Fan construction

ABSTRACT

A fan construction suitable for cooling internal combustion engines has flexible blades clamped on the inside faces of the spider arms, each blade having a hinge section in the form of a tapered bead or corrugation extending along its length with the concave part of the bead facing the spider arm so that both longitudinal edges of the bead engage the arm over a substantial portion of the length of the blade.

United States Patent Kelly [451 Oct. 17, 1972 [541 FAN CONSTRUCTION [72]Inventor: John C. Kelly, 1320 Kathmar,

Jackson, Mich. 49203 [22] Filed: Feb. 1, 1971 [2]] Appl. No.: 111,586

[52] U.S. Cl ..416/l32, 416/240 FOREIGN PATENTS OR APPLlCATlONS 559,6749/1932 Germany ..416/240 12,846 .1909 GreatBritain..., ..416/240 PrimaryExaminerEverette A. Powell, Jr. Attorney-Harness, Dickey & Pierce [57]ABSTRACT A fan construction suitable for cooling internal combustionengines has flexible blades clamped on the inside faces of the Spiderarms, each blade having a hinge section in the form of a tapered bead orcorrugation extending along its length with the concave part of the beadfacing the spider arm so that both longitudinal edges of the bead engagethe arm. over a substantial portion of the length of the blade.

7 Claims, 6 Drawing Figures PATENTEMBI 11 I872 INVENTOR. 02%;? C. 4 6

FAN CONSTRUCTION SUMMARY OF THE INVENTION It is the purpose of theinvention to improve the design of flexible blade type fan constructionsso as to stiffen the blades against undesired vibration or flexing and,at the same time, provide a controlled and better flexing action.

The invention accomplishes this purpose through the use of a beaded orcorrugated section extending lengthwise of the fan blade. This sectionacts as a hinge to permit the blade to flex transversely in a controlledmanner and also acts as longitudinal rib means to stiffen the blade toflex transversely in a controlled manner and also acts as longitudinalrib means to stiffen the blade against undesired longitudinaldeflection.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing aflexible fan constructionembodying the invention mounted on an internalcombustion engine (shown in phantom);

FIG. 2 is an enlarged view of one of the fan blades of FIG. 1, mountedon its spider, as viewed from the back of the fan construction, i.e., asseen from the left or rear of the engine of FIG. 1;

FIG. 3 is an enlarged cross section along the line 3- 3 of FIG. 2;

FIG. 4 is an enlarged cross section along the line 4- 4 of FIG. 2;

FIG. 5 is a schematic side view of one of the fan blades mounted on aspider arm with plate 31 omitted; and

FIG. 6 is a schematic view similar to FIG. 3 but with plate 31 omittedshowing a modified form of hinge structure.

DESCRIPTION OF THE INVENTION In FIG. 1 the internal combustion engine 1includes an axial flow fan construction 3, embodying the presentinvention, that has a plurality of flexible fan blades 5 mounted on thearms 7 of a spider 9 which includes a hub section 11 that is secured bybolts 13 to a rotary part of the engine 1. The bladesS are made ofelastically flexible material, preferably metal but certain plastics arealso feasible, and are, in general, constructed and mounted in such away that upon rotation of the fan 3 in the direction of the arrow 15 airwill be pumped in a direction parallel to the rotary axis 16 of the faninwardly or toward the rear of the engine 1. To provide a pitch toaccomplish this movement of air, the spider arms 7 are twisted or curvedas seen in FIG. 6 so that their leading edges 17 are axially forward oftheir trailing edges 19 and the blades 5 each have a rearwardly curvedtrailing section 21.

In operation, the blade sections 21 are subjected to pressure acting inthe direction of arrow 23 which is proportional to the speed of rotationand tends to axially flax and flatten them or reduce their pitch. Asthey flatten, they pump less air and use less horsepower to therebyincrease the efficiency of operation of the engine 1. Repeatedflattening or flexing of the blades 5 introduces fatigue stresses intothe blades and their connections with the spider arms 7 that may lead toearly failure. Accordingly, it is one of the objects of the presentinvention to provide a fan blade construction, and connection with thespider arm, that distributes the stresses on the blade and on theconnection so as to lower the maximum stress levels and thereby increasethe life of the fan construction.

As seen best in FIG. 2 each fan blade 5 comprises a longitudinallyextending side portion 25 which is transversely coextensive with andoverlapping the spider arm 7 to which it is attached. Extendingtransversely from the attachment portion 25 is the curved downstreamtrailing edge section 21. The attachment portion 25 is secured againstthe downstream face 27 of the spider arm 7 by means of a series ofrivets 29 or the equivalent, the rivets preferably seating against aclamp plate 31 which is somewhat less in thickness than the spider arm 7as can be seen in FIG. 3. As can be seenin FIG. 2 the outer longitudinalend of the fan blade 5 may extend beyond the outer end of the arm 7. Itis desirable, however, that the overlap section being of sufficientlength to provide the necessary strength of connection between the bladeand spider arm and a degree of stiffness against deflection of the blade5 about an axis transverse to its length.

In accordance with this invention, the attachment section 25 of the fanblade is provided with a hinge means 33 for deflection of the trailingedge section 21 that is integral with and formed as a part of astructure of the blade 5. In FIGS. 2 to 4 the hinge means 33 is in theform of a single arcuate corrugation or bead 35 which extends the fulllength of the blade5. The bead 35 extends in a downstream direction andsince the fan blade 5 is attached to the downstream spider arm face 27the bead 35 is concave on its upstream surface whereby it is spaced fromthe surface 27 as seen by the channel 37. The outer end of the channel37 is preferably open whereas the inner end is preferably substantiallyclosed by bending of a flap 39 across the inner end of the bead 35.Preferably, and as shown in FIGS. 3 and 4, the head 35 is uniformlytapered with respect to its depth or height so that the outer end isconsiderably deeper than the inner end, the width preferably beingconstant throughout the length of the bead.

The curved side edges on the leading and the trailing sides of the bead35 have lines of tangency 41 and 43 with the surface 27 of the spiderarm 7. The line 43 is preferably located inwardly from the side edge 47of the arm 7 by about one-eighth inch in the average size fanconstruction used on modern U.S. automobiles. The lines 41 and 43 alongwith the center line 45 of the head 35 (i.e., the line defined by thepoints at, which curvature of the circular bead sections reverse)constitute the axes about which the trailing edge 21 of the blade willflex as it moves under the variation of pressure indicated by the arrow23. Thus, the fixed end or side condition on the attachment side 25 ofthe blade 5 as the section 21 deflects in the manner of a cantileverincludes three transversely spaced parallel axes 41, 43, and 45 insteadof a single axis as is commonly the condition under cantilever loading.Accordingly, the stress level and the possibility of fatigue failure areminimized. The head 35 also stiffens the blade 5, particularly withrespect to longitudinal deflection or vibration in a plane perpendicularto arm 7. The tapered shape of the bead 35 provides for a more uniformstress distribution along the length of the blade 5.

FIG. 6 shows a modified form of hinge means 51 attaching the fan bladeto the spider arm 71 wherein a pair of parallel beads 53 are pressedinto the sheet from which the blade 7 is formed. These act in accordancewith the principles described to furnish a plurality of hinge axes toaccommodate cantilever deflection of the blade 5' as a result ofpressure variation 23 on the blades.

Modifications in the specific structure shown may be made withoutdeparting from the spirit and scope of the invention.

lclaim:

1. An axial flow flexible fan construction of the type used on variablespeed engines comprising a rotatable spider having an axis of rotationand arms extending radially with respect to said axis and fan bladessecured along a line of attachment to said arms and inducing fluid flowin a direction parallel to said axis, said blades each comprising anattachment side portion overlapping said arm and a trailing edge sideportion extending away from said arm and attachment portion, saidattachment portion including a corrugated flexible hinge section spacedfrom said line of attachment extending the full length of the blade andforming the fixed side about which the blade deflects due to variationsin fluid pressure on the blade, said attachment portions being securedto the downstream sides of the arms.

2. A fan construction as set forth in claim 1 wherein said hinge sectionengages the arm along at least two lines of tangency and said trailingedge section deflects about said lines as axes of deflection and alsoabout a line located centrally between said lines of tangency.

3. A fan construction as set forth in claim 2 wherein said hinge sectioncomprises a single arcuate bead.

4. A fan construction as set forth in claim 3 wherein said bead variesuniformly in size from the inner to the outer ends of the blade.

5. Afan construction as set forth in claim 4 wherein said bead is ofconstant'width but tapered in depth so that its shallow end is at theinner end of the blade.

6. A fan construction as set forth in claim 5 including meanssubstantially closing the inner end of the channel-formed by the bead.

7. A fan construction as set forth in claim 1 wherein said hingesections each comprises a plurality of parallel ribs tangent along aplurality of lines with the downstream side of the arm to which it issecured.

1. An axial flow flexible fan construction of the type used on variablespeed engines comprising a rotatable spider having an axis Of rotationand arms extending radially with respect to said axis and fan bladessecured along a line of attachment to said arms and inducing fluid flowin a direction parallel to said axis, said blades each comprising anattachment side portion overlapping said arm and a trailing edge sideportion extending away from said arm and attachment portion, saidattachment portion including a corrugated flexible hinge section spacedfrom said line of attachment extending the full length of the blade andforming the fixed side about which the blade deflects due to variationsin fluid pressure on the blade, said attachment portions being securedto the downstream sides of the arms.
 2. A fan construction as set forthin claim 1 wherein said hinge section engages the arm along at least twolines of tangency and said trailing edge section deflects about saidlines as axes of deflection and also about a line located centrallybetween said lines of tangency.
 3. A fan construction as set forth inclaim 2 wherein said hinge section comprises a single arcuate bead.
 4. Afan construction as set forth in claim 3 wherein said bead variesuniformly in size from the inner to the outer ends of the blade.
 5. Afan construction as set forth in claim 4 wherein said bead is ofconstant width but tapered in depth so that its shallow end is at theinner end of the blade.
 6. A fan construction as set forth in claim 5including means substantially closing the inner end of the channelformed by the bead.
 7. A fan construction as set forth in claim 1wherein said hinge sections each comprises a plurality of parallel ribstangent along a plurality of lines with the downstream side of the armto which it is secured.